Antenna system with electronic scanning means



Sept. 20, 1966 J BLASS 3,274,601

ANTENNA SYSTEM WITH ELECTRONIC SCANNING MEANS Filed Dec. 12, 1962 5Sheets-Sheet 1 30-2 INVENTOR.

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ANTENNA SYSTEM WITH ELECTRONIC SCANNING MEANS Filed Dec. 12, 1962 5Sheets-Sheet 2 INVENTOR.

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ANTENNA SYSTEM WITH ELECTRONIC SCANNING MEANS Filed Dec. 12, 1962 5Sheets-Sheet 5 J15. 4L M 3/ *2 56 E r E. 5..

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Own? E/ k, F0550, Qaes {Jaw/v X A r fawn m Sept. 20, 1966 J BLASSANTENNA SYSTEM WITH ELECTRONIC SCANNING MEANS Sept. 20, 1966 ANTENNASYSTEM WITH ELECTRONIC SCANNING MEANS Filed Dec. 12, 1952 J BLASS 5Sheets$heet 5 United States Patent 3,274,601 ANTENNA SYSTEM WlTHELECTRONIC SCANNING MEANS Judd Blass, Bayside, N .Y., assignor to BlassAntenna Electronics Corporation, Long Island City, N.Y., a corporationof Delaware Filed Dec. 12, 1962, Ser. No. 244,089 17 Claims. (Cl.343754) This invention relates to antenna systems and more particularlyto a technique for scanning the beam of a reflective antenna systemwithout physically moving either the reflector or feed. Such scanning isobtained in a prefera-ble manner by the cooperation of the signal feedwith a novel reflecting surface formed of a plurality of interrelatedradiating elements. The phase of the signals established by individualones of the radiating elements may be rapidly switched to cause thecontour of the reflecting surface to electrically vary, therebyeffecting scanning of the antenna beam through a sector in space.

Directive antennas are used in a variety of narrow beam systems, such asconventional radar installations, to accurately determine the angularposition of a target under investigation. Such systems generally mustinclude a means for positioning a narrow beam of energy about a muchwider scan angle in space. One well known method for obtaining antennabeam scanning is to move the reflector mount structure itself toappropriately direct the secondary beam in the desired direction.Another technique utilizes a feed horn slightly off center with respectto the principal axis of a parabolic reflector. The feed horn is thenphysically moved about a small area concentric with the focus of thereflector. Such movement of the feed horn similarly rotates the axis ofdirectivity of the secondary beam. Because of system inertia and othermechanical difliculties encountered with movement of the reflector orfeed itself, such prior art systems have been severely limited as toscanning rates and accuracy.

Other prior art arrangements have been formed of various arrays ofindividual amplifier and radiating element pairs, electrically connectedby separate transmission lines. The energy fed to each of the radiatingelernents is judiciously phase adjusted to have a uniform phasevariation between adjacent elements. If the phase is made toprogressively differ along the array, the energy maximum will not occurin the direction of the principal axis, but rather at some angle withrespect there-to. Accordingly, the direction of major response of theantenna can be swept across a sector of space by proper variation of thephase between the individual radiating elements of the array. Suchsystems have typically been quite complex, space consuming and haveexhibited severe limitations as to scan angle rate, switching techniquesand energy loss.

Another method of scanning a beam utilizes a line source of energy whichis capable of having a uniform phase variation along its length. Such aphase variation may be obtained by relative movement of the feed sourcemembers, with one such arrangement utilizing a rotating or oscillatingprism intermediate the line source and the radiators. Another lineararray arrangement has been obtained by mechanically varying the pathlengths along a line source beam, as employed in the well known Fosterscanner (shown in US. Patent No. 2,832,936). Other linear array scanningsystems have been constructed to vary the phase between slots along awave guide or coaxial line by reciprocating motion of the waveguidewalls or rotation of a specially constructed linear coaxial conductor.Besides exhibiting the aforementoned mechanical difliculties, suchpreviously practiced linear arrays have demonstrated high mismatch, lossin gain, and limitation 7 as to possible sc-an angles and beam focussingcapabilities.

3,274,601 Patented Sept. 20, 1966 A preferred linear array system may beconstructed in the manner shown in my copending US. patent application(M-877) entitled Antenna System," Serial No. 230,- 358, filed Oct. 15,1962. That patent application shows a simplified arrangement of parallelfed radiating elements coupled to a main signal channel in the manner ofa traveling wave array, with the individual path lengths between themain signal feed and the individual radiators electrically variable inan extremely simple manner, to point a narrow beam of energy in adesired direction. Such a system, however, will still exhibit beamfocusing limitations.

My invention avoids the limitations of the prior art systems by theutilization of a novel concentrating reflector in conjunction with asignal feed located at the focal region thereof. The reflecting surfaceis formed of a plurality of individual phase controlled radiatingelements operating in the manner of a phased backscatter array. Therelative phase of individual wave signals formed at the reflectingsurface are individually and rapidly controllable in a simplified manner(as, for example, in the order of a few nano-seconds (1(l seconds)) toelectrically analogize the reflecting surface and signal feed to aconventional parabolic system scanned to the desired direction. That is,the phase control circuitry associated with the individual radiatingelements additively changes the electrical con-tour of the reflectingsurface to reposition its axis of directivity. Thus, my inventionpermits the scanning of a concentrated beam formed by the cooperation ofa reflecting surface and a signal feed, Without requiring physicalmovement of either the feed or the reflecting surface. Further, thefocal point is not restricted by the geometry of the system, but may bearbitrarily located.

In a preferred embodiment of my invention the reflecting surface isformed of a plurality of individual radiating elements, such asopen-ended ridge waveguides, arranged about a planar area to form arectangular matrix; the matrix being referrable to orthogonally relatedaxes. Each of the radiating elements is electrically connected toindividual, but electrically associated wave channels of a novel phaseshift network. The novel phase shift network comprises separate branchsignal channels, such as ridged Waveguides, for each of the radiatingelements. The radiating elements are at one end region of the branchsignal channels and an adjustable microwave short at the other endregion.

The radiating elements forming the reflecting surface can be of anynumber or type (e.g. small horns flush mounted dipoles), consistent withthe requirements of the radiating apertures. The design of theseelements and their location about the antenna apertures region iscarefully chosen so as to maximize the capture efliciency and minimizethe energy which is lost as direct reflections or scatter. As forexample, I have obtained particularly favorable results from spacing theindividually radiating elements approximately /2 wavelength apart at themean frequency of operation.

Although for purposes of explanation, the ensuing discussion isprincipally directed to the transmit mode of operation, it is to beunderstood that an analogous condition prevails for receive-r operation.Hence, the antenna system of my invention is equally adaptable for boththe transmit and receive mode.

The Wave signal energy of each branch signal channel which is originallyincident on their respective radiating elements is first directedbackwards along the length of the branch signal channel until itencounters the microwave short circuit at the second end region. Thesignal is then oppositely directed back towards the first end region,wherein it is propagated into space by the radiating element. Themicrowave short circuit is longitudinally adjustable along the secondend region of the branch signal channel, such that the path lengthtraveled by each of the wave signals is independently adjustable. Thephase of the wave signal reflected back to the radiating element willaccordingly be determined by the above described path length traversed.Hence, the repositioning of the shorting element along the second endregion of the branch signal channel will accordingly introduce a phaseshift adjustment in the wave signal propagated by its associatedradiating element.

In a practical antenna built in accordance with my invention, it isoftentimes desirable to include a great number of individuallycontrollable radiating elements (which may be up to or in excess of10,000). A particularly advantageous aspect of my invention is thesimplified manner in which I provide individual adjustment of such alarge number of branch circuit shorting elements. Whereas the phasedarrays of the prior art typically must includes rather expensive andcomplex arrangements to effect the proper phase differential between theadjacent radiating elements, my invention preferably provides suchvariation by the digital control of switching diodes. The diodes aredigitally switched in a simplified and inexpensive manner into theirconducting or blocking states, the former effecting a short circuitcondition across the branch signal guides. I have observed that properprogramming of only four such shorting diodes in each branch signalchannel is adequate to obtain a sharply defined and accuratelypositioned beam. Such a four diode adjustable short permits asubstantial simplification in the manner in which the individual pathlengths may be varied to obtain the requisite progressive phase shiftfor beam scanning. A two bit flip flop circuit is advantageouslyemployed as the phase adjusting means, with the fl-ip flop outputsconnected to the shorting diodes to provide the necessary bias potentialfor switching. Hence, my switching technique preferably avoids the useof multiple receivers, transmitters or ferrite phase shifters astypically employed in the phased array systems of the prior art.

As another aspect of my invention, the orthogonal matrix of theindividual radiating elements permits a substantial simplification inthe generation of the scan control signals. It is well known in the artthat the phase distribution of such a planar array whose individualelements are arranged in a rectangular matrix can be separated as thesum of two independent phase distributions corresponding to theorthogonal axes of the array. Accordingly, where a large number ofindividual radiating elements are to be used, the scan control generatorreferable to each axis need only provide the square root of the numberof phasing signals as there are radiating elements. These signals arefed to binar add circuits individual to each adjustable short. Thebinary adding circuits as well as the flip flops are commerciallyavailable in relatively inexpensive, highly compact and extremelyreliable assemblies, to thereby provide trouble free operation.

For increased accuracy the orthogonally related scan control signalspresented to the inputs of the binary add circuit are advantageouslythree-bit digital signals. Each of the diodes are positioned to effectan overall 90 phase differential in the path length. Hence, digitaloutputs of the add circuit which correspond to fractions of a 90differential or to multiples of a 360 differential may be dropped.Accordingly, the sum of the three-bit digital signals need only bytransposed as a two-bit signal, which signals additively effect anaccurate positioning of the antenna system beam. As a furtherrefinement, a spherical correction factor may be interposed intermediatethe scan control signal generator and the binary add circuit whichpresents the two-bit digital signal to the flip flop control of theshorting diodes. Particularly advantageous operation is obtained byemploying a digital scan control system for switching the adjustmentmeans of the four position diode shorts. That is, in previous systemsemploying analog control networks the presence of noise or otherextraneous signals within the system resulted in an inaccuracy in thebeam position, thereby limiting its application for high precisionlobing. By properly designing the flip flop switches of my controlsystem, such extraneous signals will be below the threshold switchinglevel. Thus, they will have substantially no effect on the digitaloutput signal, and therefore will not cause an improper positioning ofthe scan angle.

It is thus seen that the basic concept of my invention resides .informing the reflecting surface of an antenna system of a plurality ofradiating elements, each associated with an individual branch signalchannel. The branch signal channels include an adjustable short to varythe phase of their respective signals at the reflecting surface. Thereflecting shorts of the individual branch signal channels may berapidly switched to provide for rapid and accurate scanning of thefocused antenna beam formed by the additive eflect of the branchsignals.

It is therefore a primary object of this invention to provide asimplified, rapid and accurate reflective antenna scan system.

A further object of this invention is to provide an antenna scan systemwherein the reflecting surface operates in the manner of a conventionalparabolic reflector in conjunction with a signal feed at the focalregion thereof, which may be electrically scanned without physicalmovement of either the reflector or the signal feed.

Another object of this invention is to provide an antenna scan systemhaving a reflecting surface formed of a predetermined array ofindividual radiating elements, each electrically associated with anindividual wave signal channel having an adjustable short at theopposite end thereof.

An additional object of this invention is to provide such an antennasystem wherein the adjustable short is electrically controlled such thatthe additive phase effect of the radiating element signals willcontrollably position the antenna beam in a desired direction.

Still a further object of this invention is to provide such a reflectiveantenna system wherein the shorting elements are rapidly adjustable tomodify the phase of the emergent signal such that the scan angledetermined by the additive phase effect of the individual radiatingelements produces a concentrated beam of energy adjustable in direction.

Still another object of this invention is to provide a reflectiveantenna scanning system wherein the reflecting surface is formed of amatrix array of individual radiating elements, the phase of each of thesignals established by the radiating elements being controllable byorthogonally related digital signals.

Still an additional object of this invention is to provide a reflectiveantenna system including controllable signal reflecting means formed ofindividual shorting diodes, bias switched between their conducting andnon-conducting states by the output potential of a two-bit digitalcircuit to provide beam scanning.

These as well as other objects of the instant invention will readilybecome apparent after reading the following description of theaccompanying drawings in which:

FIGURE 1 is a perspective view of an antenna system constructed inaccordance with the teachings of my invention.

FIGURE 2 is a partially broken away perspective view of a portion of thereflecting surface, showing the adjacent positioning of the radiatingelements, the branch signal wave guides, and the adjustable reflectingmeans.

FIGURE 3 is a simplified schematic illustration showing the basicoperation of the phase shift adjust of each of the branch 'signalchannels.

FIGURES 4 and 4a are end and cross-sectional views respectively of ashorting diode array which may be used in conjunction with my invention.

FIGURE 5 is a simplified schematic representation of the operation :ofan individual diode shorting element.

FIGURE 6 schematically shows the spaced relationship between the antennabeam orientation and the orthogonally related axes of the radiatingelement array.

FIGURE 7 is a block diagram illustrating the matrix arrangement of thescanning generator and the individual binary add circuits of theadjustment control means.

FIGURE 8 is a block diagram showing the interrelationship of the scancontrol generator, the binary add circuit, the switching flip flop andthe individual diode switches.

FIGURE 9 is a block diagram similar to FIGURE 8, but showing theaddition of a means for spherical correction.

FIGURE 10 shows an alternative embodiment of the radiating elements,which are shown as comprising individual dipoles.

FIGURES 11 and 12 are plan and elevation views respectively of a phaseback scatter array antenna system constructed in accordance with theteachings of my invention, which utilizes three independent reflectingsurfaces and signal feeds for hemispheric scan coverage.

Referring to the figures and FIGURES 1 and 2 particularly, antennasystem comprises a reflecting surface and a signal feed 40. Reflectingsurface 30 is formed of a plurality of adjacently positioned radiatingelements 32 forming a generally planar surface mounted to stationaryplatform 48. Feed 40 is appropriately secured to the reflecting surfaceby side supports 42. Transmission line 44 interconnects feed 40 to areceiver or transmitter (not shown), to effect operation in either thetransmit or receive mode. Radiating elements 32 are typically shown asopen end ridge wave guides. Altern-atively the radiating elements may besmall horns or dipoles constructed to be electrically consistent withthe requirements of the particular antenna system. In the particularexample shown in FIGURES 1 and 2, they are open ended ridge wave guideshaving a center to center separation approximately one-half wavelengthat the mean operating frequency. Each of the radiating elements 32 arelocated at a first end region of an individual branch signal channel 34,such branch signal channel being illustratively shown as a ridgedwaveguide. The phase of the individual branch signals at 32 areindividually varied by an adjustable reflecting means generally shown at50, one form of which is shown in FIGURES 4 and 5. The radiatingelements 32 are positioned such that the phase of the individual signalsassociated therewith may lbe progressively shifted by beam director unit80, in the manner to be subsequently discussed, to electrically form aparabolic surface at 32 in conjunction with feed 40. Pin 33 is shown forimproved impedance matching. Fiber glass radome may also be included forenvironmental protection.

As is well known in the art, the direction of a beam generated by suchan array of individual radiating elements 32 is determined by the phasecorrespondence of the individual signals; that is, the scan angle of theantenna beam will be in that direction which corresponds to phasecoincidence of the individual radiating elements. Accordingly, by propercontrol of the phase of each of the signals associated with theindividual radiating elements 32, an additive eflect is obtained, suchadditive effect being controlled to provide scanning of the concentratedantenna beam. Such control is obtained by sequentially related digitalsignals of a beam director unit 80, which signals are shown presented byharness runs 60 to the individual adjustable reflecting means 50. Signalfeed is appropriately designed to illuminate the surf-ace 30 with aminimum of spillover. Thus, the wave signal provided by feed 40 ispicked up by radiating element 32 and directed towards its opposite endregion of branch wave signal channel 34. If channel 34 were terminatedin a matched load, the power dissipated by such a load would exactlyequal the power re-radiated by the parasitic current associated withradiating element 32. The radiation pattern of such parasitic currentswould be the image of the incident wave, and hence exhibit limiteddirectivity. However, if branch signal channel 34 is short-circuited at50, the signal which travels down the line will be reflected at suchshort circuit, and directed back towards radiating element 32, where itis radiated into space. Thus, in the short circuited case, the radiationfield consists of the parasitic current plus the back scatter radiationfrom the current which travels down, to, and back from the reflectingmeans; the phase of the back scatter component being equal to twice theelectrical length from the radiating element 32 to the short circuit. Inaccordance with my invention a progressive phase shift is obtainablebetween adjacent radiating elements by proper adjustment of the shortcircuit positions to therefore collimate the individual branch wavesignals into a pencilled beam. The additive phase eifect of the beam issteerible in space by appropriate adjustment of the reflecting means.

Reference is now made to FIGURE 3, which shows in a simplified mannerthe basic operation of the phase shift adjust provided by the reflectingmeans 50 in each of the branch signal channels 34. The operation of onlyone such channel is shown with it being understood that an analogousmode of operation is obtained in each of the other channels. End 31 ofthe branch wave signal channel includes an adjustable reflective short50 which is preferably shown as a longitudinally positioned array ofindividual diode elements 56. It is to be noted that these shortcircuits need not be diodes or be discreet. Alternatively, theseelements may be any other device well known in the art to provide anadjustable reflecting surface, such as a sliding metal shorting plunger.However, the diode arrangement shown preferably permits a switchingarrangement in a more simplified and rapid manner than has heretoforebeen available, permitting optimum electronic performance. Four suchdiode elements 561 to 56-4 are shown which may be appropriately switchedbetween their conducting and blocking states to selectively position theshort within each of the branch channels. Incident energy A, uponreaching the shorted diode, illustratively shown as 563, is reflectedand directed back towards end 32, as shown by arrow B (shown dotted forpurposes of clarity). The phase of reflected wave B is accordinglydependent upon which of the individual diodes is shorted. Inasmuch asthe signal within the branch signal channel traverses a path in anupand-down direction towards short 50, each of the diode elements 56 areseparated by one-eighth of a wavelength at the mean operating frequencyof the antenna system, to provide a one-quarter wavelength overall pathdiflerential to the branch waveguide signal.

FIGURES 4, 4A and 5 illustrate a preferred configuration and schematicrepresentation of the diode shorting elements 56. All of the elements 56of a shorting switch array 50 are disposed within a longitudinaldielectric tube 53 to facilitate insertion and rem-oval of the switchingarray as a unit intermediate waveguide walls 58 and ridge 55. Thewaveguide walls and ridge 55 are at ground potential. The anode terminal57 of diode element 56 is shown connected to one of the wall surfacesvia metallic insert 61 in the dielectric tube. The cathode terminal 59of the diode is connected to a positive D.C. bias, which may typicallybe one of the outputs of flip flop control 98 (FIGURE 8). The D.C. biaspresented by the flip flop output to the cathode 59 is of a suflicientmagnitude to place the diode in its blocking state, thereby providing anopen circuit. Removal of the D.C. bias places diode 56 in its conductingstate, thereby providing a reflective short to the incident microwavesignal. Capacitive element 62 is provided for RF bypass of the biasreturn 63. It is thus seen that the individual diodes 56 areconveniently contained within a compact unitary structure which may be 7easily inserted and properly positioned within the end region 31 of theindividual branch wave channels.

Reference is now made to FIGURE 6 which shows the relative orientationbetween the radiating elements 32 and the beam direction Radiatingelements 32 are shown adjacently positioned to form a rectangular matrixin the plane defined by orthogonally related axes x and y. It is wellknown that the phase distribution of a planar antenna whose elements arearranged in a rectangular matrix as shown in FIGURE 6 can be separatedas the sum of two independent phase distributions, each varyingaccording the cosine of the angles from the orthogonally related axes(alpha and beta). Accordingly, FIGURE 7 illustrates such a matrixwherein beam director unit 80 presents appropriate signals to the x andy scan control generators 70, 75 respectively. The output signals of thescan control generators 70, 75 are presented to x and y scan controlnetworks 90, 95 respectively. These networks may typically be anarrangement of conventional digital circuitry to provide properly phasedelayed signals along the x and y axes. Alternatively, a-f delay linenetworks may be used to phase control the individual branch signal wavesto cumulatively yield the desired scan angle. The output signals of thescan control networks 90, 95 are presented as input signals to binaryadd circuits 96, each located at the x-y intersection of theircorresponding radiating elements 32. The binary add output signals willaccordingly be correlated to position the antenna beam in the desireddirection 1).

Referring to FIGURE 8, the signal provided by x and scan controlgenerators 70, 75 to the binary add circuit 96 is preferably athree-digit signal. Such a three-digit signal provides additionalprecision of the sum signal presented by add circuit 96 to flip flop 98.The sum signal output of the binary add circuit 96 may, however, dropthose digits corresponding to integral multiples of a wavelength andless than a quarter wavelength variation. Hence, the sum obtained byadding the three-digit input signals may be transposed to a two-digitsignal for operation of the four position shorting diode array 56-1 to56-4.

In a typical case the input signals presented by each of the scancontrol networks 70, 75 do not correspond to exact multiples of thequarter wave delay obtainable by the four position shorting switch.Thus, where an intermediate amplitude signal is presented, the phaseshift of its associated branch signal circuit might not exactlycorrespond to that theoretically required for a desired scan angle.However, it has been found that by providing a suflicient number ofbranch channels and associated radiating elements in the overall antennasystem, the cumulative effect of these slight deviations tend to cancel,thereby giving a scan angle accurately related to the signal generatedby beam director unit 80.

Referring to FIGURE 9 it is seen that an additional digitally controlledsignal 97 may be provided intermediate binary add circuit 96 and flipflop 98, to provide appropriate spherical correction. Signal 97 ispresented as one input to an intermediate binary add circuit 99, whichcircuit receives a three-bit output sum signal from binary add circuit96 as its other input. Hence, the system schematically shown in FIGURE 9provides beam scanning in conjunction with a tunable sphericalcorrection factor.

Digital control of the individual branch signal phase shift ispreferably used to reduce the susceptibility of antenna system 20 toerrors caused by the generation of noise or other extraneous signalswithin the circuitry. That is, the circuitry can be appropriatelydesigned such that the digital switching amplitude is kept substantiallyabove any such extraneous signal. Therefore, the presence of thesesignals will not have an effect on the output count of flip flops 98 andhence the phase shift of the individual branch circuits 34. This permitsextreme accuracy in the beam position and affords my inventionparticular utility for high precision, high frequency lobing.

FIGURE 10 shows a modified arrangement of the radiating elements 32'which comprise the reflecting surface 30'. These elements are shown asbalanced dipoles connected to branch wave signal channels 34' formed ofcoaxial transmission lines. Appropriate impedance transformer sections37, such as a Balun-dipole to coaxial line transformer, are interposedintermediate the radiating dipole 32 and the coaxial line 34'. Areflecting ground screen 32" operates in conjunction with the individualdipoles 32' and is preferably located a quarter wave length therefrom.Short circuit elements 50 are of the same general type discussed abovewith appropriate dimensional changes to permit their use in conjunctionwith the coaxial line 34. The feed horn, antenna structure and scancontrol used in conjunction with this embodiment may be the same asdiscussed above since these system components are essentiallyindependent of the array element and its transmission line accessories.

Reference is now made to FIGURES 11, 12, which show three separateantenna systems 201, 20-2 and 20-3, each generally of type 20 discussedabove. Each of the systems contain a reflecting surface 30-1, 30-2, 30-3respectively, operating in conjunction with respective signal feeds40ll, 402, 40-3. The use of three such independent antennas may beappropriately correlated to provide hemispheric scan coverage.

It is thus seen that I have provided a novel antenna system whereby aconcentrated antenna beam formed by a parabolic type reflecting surfaceand signal feed may be appropriately scanned without physical movementof the antenna feed or reflecting surface. Accordingly, the focal pointscan be arbitrarily fixed and are not restricted by the geometry of theantenna, as is the case of a simple reflector or lens. Further, severalsignal feeds at different locations may be used in conjunction with asignal reflecting surface to provide increased performance capabilities.

A practical antenna system constructed in accordance with the teachingsof my invention may be, for example, constructed to operate within thefrequency range of 2800 megacycles to 3400 megacycles, having a 2 /2beam width rapidly adjustable within a sector in all planes. It ispossible to obtain 33 db of gain with the side lobes being maintainedbelow 20 db. It is naturally understood that these operatingcharacteristics are merely given for illustrative purposes and shouldnot be construed as limiting the scope of my invention. Accordingly,although I have described preferred embodiments of my novel invention,many variations and modifications will now be obvious to those skilledin the art, and I prefer therefore to be limited not by the specificdisclosure herein but only by the appended claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. In combination in an antenna system, a reflecting surface and asignal feed; scanning means cooperatively associating said reflectingsurface with respect to said signal feed to effect an antenna beamorientation in a desired direction; said reflecting surface formed of aplurality of radiating elements, each associated with a branch signalchannel; said radiating elements operatively positioned with respect tosaid signal feed to present a plurality of branch Wave signalstherebetween; said radiating elements positioned at a first end regionof said branch signal channels; individual signal reflecting means at asecond end region of each of said branch signal channels; said branchwave signals traversing a path from said radiating elements at saidfirst end region, towards said second end region, and from saidreflecting means at said second end region oppositely directed backtoward said first end region; adjusting means individually controllingthe characteristics of said plurality of reflecting means whereby thephase of said branch wave signals at each of said first end regions maybe individually varied; the additive phase effect of said branch wavesignals es- 9 tablishing said desired direction of antenna beamorientation, said reflecting means including shorting means, saidadjustment means selectively positioning said shorting means along thesecond end region of said branch signal channels, whereby the overalllengths of selected ones of said branch signal paths are varied.

2. In combination in an antenna system, a reflecting surface and asignal feed; scanning means cooperatively associating said reflectingsurface with respect to said signal feed to effect an antenna beamorientation in a desired direction; said reflecting surface formed of aplurality of radiating elements, each associated with a branch signalchannel; said radiating elements operatively positioned with respect tosaid signal feed to present a plurality of branch wave signalstherebetween; said radiating elements positioned at a first end regionof said branch signal channels; individual signal reflecting means at asecond end region of each of said branch signal channels; said branchwave signal-s traversing a path from said radiating elements at saidfirst end region, towards said second end region, and from saidreflecting means at said second end region oppositely directed backtoward said first end region; adjusting means individually controllingthe characteristics of said plurality of reflecting means whereby thephase of said branch wave signals at each of said first end regions maybe individually varied; the additive phase effect of said branch wavesignals establishing said desired direction of antenna beam orientation,said reflecting means including shorting means, said adjustment meansselectively positioning said shorting means along the second end regionof said branch signal channels, whereby the overall lengths of selectedones of said branch signal paths are varied; said reflecting meanscomprising a group of diodes positioned along the second end region ofsaid branch signal channel; each of said diodes having a conducting and.a blocking state; said diodes when in said conducting state providing areflective short to said couple energy; said adjustment means presentinga biasing signal to said diode elements whereby switching said diodeelements between said conducting and said blocking states.

3. In combination in an antenna system, a reflecting surface and asignal feed; scanning means cooperatively associating said reflectingsurface with respect to said signal feed to effect an antenna beamorientation in a desired direction; said reflecting surface formed of aplurality of radiating elements, each associated with a branch signalchannel; said radiating elements operatively positioned with respect tosaid signal feed to present a plurality of branch wave signalsthe-rebetween; said radiating elements positioned at a first end regionof said branch signal channels; individual signal reflecting means at asecond end region of each of said 'branch signal channels; said branchwave signals traversing a path from said radiating elements at saidfirst end region, towards said second end region, and from saidreflecting means at said second end region oppositely directed backtoward said first end region; adjusting means individually controllingthe characteristics of said plurality of reflecting mean-s whereby thephase of said branch wave signals at each of said first end regions maybe individually varied; the additive phase effect of said branch wavesignals establishing a reflective antenna system having a focal point atsaid signal feed corresponding to said desired direction of antenna beamorientation, said reflecting means including shorting means; saidadjustment means selectively positioning said shorting means along thesecond end region of said branch signal channels, whereby the overalllengths of selected ones of said branch signal paths are varied.

4. The antenna system of claim 1 wherein said shorting means include aplurality of individual shorting elements longitudinally separated alongthe second end region of said branch signal channel.

5. The antenna system of claim 3 wherein said shorting means comprisediode-s placed across said branch signal channel, and longitudinallyseparated to introduce a predetermined path differential of said branchsignal.

6. The antenna system of claim 3 wherein said adjustment means presentsa biasing signal to selected ones of said diodes; said biasing signalswitching said diodes between their conducting and blocking states.

7. The antenna system of claim 2 wherein each of said branch channelsinclude four of said diode elements; said adjustment means being atwo-bit digital circuit; the output signals of said digital circuitsproviding the switching bias of said diode elements.

8. The antenna system of claim 7 further including a scan control means;said scan control means presenting sequentially related digital controlsignals to said adjustment means, whereby said diode elements areselectively adjusted to control the scan angle of said antenna beam.

9. In combination in an antenna system, a reflecting surface and asignal feed; scanning means cooperatively associating said reflectingsurface with respect to said signal feed to effect an antenna beamorientation in a desired direction; said reflecting surface formed of aplurality of radiating elements, each associated with a branch signalchannel; said radiating elements operatively positioned with respect tosaid signal feed to present a plurality of branch wave signalstherebetween; said radiating elements positioned at a first en-d regionof said branch signal channels; individual signal reflecting means at asecond end region of each of said branch signal channel-s; said bran-chwave signals traversing .a path from said radiating elements at saidfirst end region, towards said second end region, and from saidreflecting means at said second end region oppositely directed backtoward said first end region; adjusting means individually controllingthe characteristics of said plurality of reflecting means whereby thephase of said branch wave signals at each of said first end regions maybe individually varied; the additive phase effect of said branch wavesignals establishing said desired direction of antenna beam orientation;said reflecting means including shorting means; said shorting meanscomprising a group of diodes positioned along the second end region ofsaid branch signal channel; each of said diodes having a conducting anda blocking state; said diodes when in said conducting state providing areflective short to said couple energy; said adjustment means presentinga biasing signal to said diode elements whereby switching said diodeelements between said conducting and said blocking states; saidradiating elements forming a matrix defined by orthogonally relatedaxes, the location of each of said radiating elements being referabletothe origin of said orthogonally related axes; seam control meansassociated with each of said orthogonally related axis to presentsequentially related digital control signals to said adjustment means.

10. The antenna system of claim 9, wherein said adjustment meansincludes a binary adding circuit; the sequentially related signals ofsaid scan control means being presented to the input of said binaryadding circuit as orthogonally related components; the output of saidbinary adding circuit forming said biasing signals for diode switching,whereby said diode elements are selectively adjusted to control the scanangle of said antenna beam.

11. The antenna system of claim 9, wherein said adjustment meansincludes a binary adding circuit; the sequentially related signals ofsaid scan control means being presented to the input of said binaryadding circuit as orthogonally related components; the output of saidbinary adding circuit forming said biasing signals for diode switching,whereby said diode elements are selectively adjusted to control the scanangle of said antenna beam; said selective adjustment of diode elementsforming said reflecting surface in the manner of a parabolic reflectorwith respect to said signal feed; said signal feed being operativelylocated at the focal point of said parabolic reflecting surface.

my 7 Hr 12. The antenna system of claim 11 wherein said scan controlmeans operatively switches said diode element to controllably vary theadditive phase eflect of said branch wave signals, to thereby vary theantenna beam orientation of said parabolic reflector and cooperatingsignal feed.

13. A scanning antenna system including a signal feed and a reflectingsurface; said reflecting surface formed of a plurality of radiatingelements; said radiating elements operatively positioned with respect tosaid signal feed to present a wave signal therebetween; a plurality ofbranch signal channels; said radiating elements positioned at a firstend region of said branch signal channels; said first end regionscollectively defining said reflecting surface; a second end region ofsaid branch signal channels including a signal reflecting means; saidwave signal forming a plurality of branch wave signals; said branch wavesignals traversing a path within said branch signal channels from saidradiating elements towards said reflecting means, and from saidreflecting means oppositely directed towards said first end region;adjustment means individually controlling the characteristics of each ofsaid refleeting means whereby the phase of said branch wave signal ateach of said first end regions may be individually varied; saidradiating elements adjacently located in a first and second direction todefine a generally planar region of said reflecting surface; said signalfeed positioned without said generally planar region, and in a wavesignal illuminating relationship therewith; the additive phase effect ofsaid branch wave signals establishing an antenna beam orientation withrespect to said signal feed in the manner of a parabolic reflector; saidradiating elements forming a matrix defined by orthogonally relatedaxes; the location of each of said radiating elements being referable tothe origin of said orthogonally related axes; scan control meansassociated with each of said orthogonally related axes to presentsequentially related digital control signals to said adjustment means.

14. A scanning antenna system including a signal feed and a reflectingsurface; said reflecting surface formed of a plurality of radiatingelements; said radiating elements operatively positioned with respect tosaid signal feed to present a wave signal therebetween; a plurality ofbranch signal channels; said radiating elements positioned at a firstend region of said branch signal channels; a second end region of saidbranch signal channels including a signal reflecting means; said wavesignal forming a plurality of branch wave signals; said branch wavesignals traversing a path from said radiating elements towards saidreflecting means, and from said reflecting means oppositely directedtowards said first end region; adjustment means individually controllingthe characteristics of each of said reflecting means whereby the phaseof said branch wave signal at each of said first end regions may beindividually varied; said radiating elements adjacently located in afirst and second direction to define a generally planar region of saidreflecting surface; said signal feed positioned without said generallyplanar region, and in a wave signal illuminating relationship therewith;the additive phase effect of said branch wave signals establishing anantenna beam orientation with respect to said signal feed in the mannerof a parabolic reflector; said radiating elements forming a matrixdefined by orthogonally related axes; the location of each of saidradiating elements being referable to the origin of said orthogonallyrelated axes; scan control means associated with each of saidorthogonally related axes to present sequentially related digitalcontrol signals to said adjustment means; said adjustment means includesa binary adding circuit; the sequentially related signals of said scancontrol means being presented to the input of said binary adding circuitas orthogonally related components; the output of said binary addingcircuit forming said biasing signals for diode switching, whereby saiddiode elements are selectively adjusted to control the scan angle ofsaid antenna beam.

15. A scanning antenna system including a signal feed and a reflectingsurface; said reflecting surface formed of a plurality of radiatingelements; said radiating elements operatively positioned with respect tosaid signal feed to present a wave signal therebetween; a plurality ofbranch signal channels; said radiating elements positioned at a firstend region of said branch signal channels; said first end regionscollectively defining said reflecting surface; a second end region ofsaid branch signal channels including a signal reflecting means; saidwave signal forming a plurality of branch wave signals; said branch wavesignals traversing a path within said branch signal channels from saidradiating elements towards said reflecting means, and from saidreflecting means oppositely directed towards said first end region;adjustment means individually controlling the characteristics of each ofsaid reflecting means whereby the phase of said branch wave signal ateach of said first end regions may be individually varied; saidradiating elements adjacently located in a first and second direction todefine a generally planar region of said reflecting surface andcollectively defining said reflecting surface; said signal feedpositioned without said generally planar region, and in a wave signalilluminating relationship therewith; the additive phase efiect of saidbranch wave signals establishing an antenna beam orientation withrespect to said signal feed in the manner of a parabolic reflector; saidreflecting means including shorting means, said adjustment meansselectively positioning said shorting means along the second end regionof said branch signal channels, whereby the overall lengths of selectedones of said branch signal paths are varied.

16. The scanning antenna system of claim 15, wherein said reflectingmeans comprises a group of diodes positioned along the second end regionof said branch signal channel; each of said diodes having a conductingand a blocking state; said diodes when in said conducting stateproviding a reflective short to said couple energy; said adjustmentmeans presenting a biasing signal to said diode elements wherebyswitching said diode elements between said conducting and said blockingstates.

17. The antenna system of claim 10 wherein each of said branch signalchannels include four of said diode elements; said scan control meanspresent orthogonally related three-bit digital signals to the input ofsaid binary adding circuit; the output signal of said binary addingcircuit being converted to a two-bit digital signal providing theswitching bias of said diode elements.

References Cited by the Examiner FOREIGN PATENTS 860,826 2/1961 GreatBritain.

HERMAN KARL SAALBACH, Primary Examiner.

R. H. HUNT, Assistant Examiner.

1. IN COMBINATION IN AN ANTENNA SYSTEM, A REFLECTING SURFACE AND ASIGNAL FEED; SCANNING MEANS COOPERATIVELY ASSOCIATING SAID REFLECTINGSURFACE WITH RESPECT TO SAID SIGNAL FEED TO EFFECT AN ANTENNA BEAMORIENTATION IN A DESIRED DIRECTION; SAID REFLECTING SURFACE FORMED OF APLURALITY OF RADIATING ELEMENTS, EACH ASSOCIATED WITH A BRANCH SIGNALCHANNEL; SAID RADIATING ELEMENTS OPERATIVELY POSITIONED WITH RESPECT TOSAID SIGNAL FEED TO PRESENT A PLURALITY OF BRANCH WAVE SIGNALSTHEREBETWEEN; SAID RADIATING ELEMENTS POSITIONED AT A FIRST END REGIONOF SAID BRANCH SIGNAL CHANNELS; INDIVIDUAL SIGNAL REFLECTING MEANS AT ASECOND END REGION OF EACH OF SAID BRANCH SIGNAL CHANNELS; SAID BRANCHWAVE SIGNALS TRAVERSING A PATH FROM SAID RADIATING ELEMENTS AT SAIDFIRST END REGION, TOWARDS SAID SECOND END REGION, AND FROM SAIDREFLECTING MEANS AT SAID SECOND END REGION OPPOSITELY DIRECTED BACKTOWARD